Light Source Using Photonic Crystal Structure

This is a divisional of U.S. application Ser. No. 17/296,373, filed May 24, 2021, which claims priority to PCT International Application No. PCT/KR2020/017939 which has an International filing date of Dec. 9, 2020 under 35 U.S.C. § 371, which claims priority to Korean Patent Application No. 10-2019-0176539, filed on Dec. 27, 2019, the disclosures of each of which are hereby incorporated by reference in their entireties.

The present disclosure relates to a light source using a photonic crystal structure, and more specifically, to a light source using a photonic crystal structure formed in a van der Waals heterojunction structure.

In a broad sense, a photonic crystal structure refers to a structure that affects the motion of a photon so that the optical properties of a material may be used. In addition, in a narrow sense, the photonic crystal structure may mean a structure that uses the optical properties of a material through a periodic optical nanostructure, and this periodic structure may be formed in 1D, 2D or 3D. The photonic crystal structure may be used in various technologies that need to confine or manipulate light, and various studies are being conducted to utilize the photonic crystal structure for optical modulation, light detection, or optical communication.

In addition, unlike the conventional light emitting diode (LED) using the band structure characteristics of the material, the luminescence mechanism of a graphene light source is based on blackbody radiation by hot electrons. In general, blackbody radiation has a very wide spectrum of wavelengths from visible light to infrared light, so that its luminous efficiency is low and there is a limit to its application to optical communication technology.

The present disclosure is to provide a light source using a photonic crystal structure capable of controlling a spatial light emitting area and a light emitting wavelength.

The problem to be solved by the present disclosure is not limited to the problems mentioned above, and other tasks that are not mentioned will be clearly understood by those of ordinary skill in the relevant technical field from the following description.

In order to solve the above technical problems, a light source using the photonic crystal structure according to the embodiment of the inventive concept includes a substrate; a heterojunction structure including a first encapsulation layer, a graphene layer, and a second encapsulation layer sequentially stacked on the substrate; photonic crystal holes vertically penetrating the first encapsulation layer, the graphene layer, and the second encapsulation layer; and first and second electrodes respectively connected to both end portions of the heterojunction structure, wherein the heterojunction structure comprises buffer areas contacting the first and second electrodes, respectively, and emission areas between the buffer areas, wherein the photonic crystal holes are provided in the emission area, wherein a width of the emission area is smaller than widths of the buffer areas.

In addition, a light source using the photonic crystal structure according to the embodiment of the inventive concept includes: a substrate; a heterojunction structure including a first encapsulation layer, a graphene layer, and a second encapsulation layer sequentially stacked on the substrate; photonic crystal holes vertically penetrating the first encapsulation layer, the graphene layer, and the second encapsulation layer; and first and second electrodes respectively connected to both end portions of the heterojunction structure, wherein the heterojunction structure comprises a first area in which the photonic crystal holes are not provided and a second area surrounding the first area, the second area in which the photonic crystal holes are regularly arranged.

The light source using the photonic crystal structure according to the embodiment of the inventive concept may cause a strong light-material interaction at the heterojunction interface using the photonic crystal structure formed in the van der Waals heterojunction structure, so that a high quality value (Q-factor) may be maintained.

In addition, the light source using the photonic crystal structure according to the embodiment of the inventive concept may adjust the spatial light emitting area and the light emission wavelength through the modification of the photonic crystal structure, so that energy efficiency may be further increased.

In order to fully understand the configuration and effects of the inventive concept, preferred embodiments of the inventive concept will be described in detail with reference to the accompanying drawings.

The inventive concept is not limited to the embodiments disclosed below, but may be implemented in various forms, and various modifications and changes may be added. However, it is provided to completely disclose the technical idea of the inventive concept through the description of the present embodiments, and to fully inform a person of ordinary skill in the art to which the inventive concept belongs. In the accompanying drawings, for convenience of description, the ratio of each component may be exaggerated or reduced.

The terms used in this specification are for describing embodiments and are not intended to limit the inventive concept. In addition, terms used in the present specification may be interpreted as meanings commonly known to those of ordinary skill in the art, unless otherwise defined.

In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, in relation to ‘comprises’ and/or ‘comprising’, the mentioned elements, steps, operations and/or elements do not exclude the presence or addition of one or more other elements, steps, operations and/or elements.

In this specification, terms such as first and second are used to describe various areas, directions, shapes, etc., but these areas, directions, and shapes should not be limited by these terms. These terms are only used to distinguish one area, direction, or shape from another area, direction, or shape. Accordingly, a portion referred to as a first portion in one embodiment may be referred to as a second portion in an embodiment. The embodiments described and illustrated herein also include complementary embodiments thereof. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a light source using a photonic crystal structure according to an embodiment of the inventive concept will be described in detail with reference to the drawings.

1 FIG. 2 FIG. 1 FIG. is a perspective view illustrating a structure of a light source using a photonic crystal structure according to an embodiment of the inventive concept.is a cross-sectional view illustrating a structure of a light source using a photonic crystal structure according to an embodiment of the inventive concept, and corresponds to a cross-sectional view oftaken along line I-I′.

1 2 FIGS.and 1 2 1 2 1 2 100 100 Referring to, a light source using a photonic crystal structure according to an embodiment of the inventive concept includes a first electrode E, a second electrode E, and a heterojunction structure HS between the first electrode Eand the second electrode E. The first electrode E, the second electrode E, and the heterojunction structure HS may be provided on the substrate. The substratemay include, for example, silicon oxide.

1 1 1 1 1 1 2 1 1 1 1 2 1 3 3 1 2 2 1 2 1 1 2 2 2 1 2 2 2 2 2 2 2 2 1 1 1 1 1 2 1 2 1 2 1 2 1 2 1 2 1 2 a c b a c b a c b a c a b c a b c The first electrode Emay contact an end portion of the heterojunction structure HS. The first electrode Emay contact one end portion of the heterojunction structure HS by an edge contact method, and thus, contact resistance may be minimized. More specifically, the first electrode Emay include a first portion Eand a third portion Eextending in the first direction Dand the second direction D, and a second portion Econnecting the first portion Eand the third portion E. The first direction Dand the second direction Dextend on the same plane and may be perpendicular to each other. For example, the second portion Emay extend in a direction having an inclination with respect to the third direction D. The third direction Dmay be a direction perpendicular to the first direction Dand the second direction D. The second electrode Emay contact another end portion of the heterojunction structure HS that faces one end portion in contact with the first electrode E. The second electrode Emay be spaced apart from each other in the first electrode Eand in the first direction D. More specifically, the second electrode Emay include a first portion Eand a third portion Eextending in the first direction Dand the second direction D, and a second portion Econnecting the first portion Eand the third portion E. The first to third portions E, E, and Eof the second electrode Emay have substantially the same shape as the first to third portions E, E, and Eof the first electrode E, respectively. However, this is only an example, and the first electrode Eand the second electrode Emay each have various shapes electrically connected to the heterojunction structure HS. The first electrode Eand the second electrode Emay include metal. For example, the first electrode Eand the second electrode Emay include any one of chromium (Cr), palladium (Pd), and gold (Au). The first electrode Eand the second electrode Emay be any one of a source electrode and a drain electrode, respectively. More specifically, when the first electrode Eis a source electrode, the second electrode Emay be a drain electrode, and when the first electrode Eis a drain electrode, the second electrode Emay be a source electrode. A voltage for the operation of the heterojunction structure HS may be applied through the first electrode Eand the second electrode E, and a current may flow.

1 2 1 2 1 2 The voltage applied through the first electrode Eand the second electrode Emay be a pulse voltage or a DC voltage. When a pulse voltage is applied to the first electrode Eand the second electrode E, super-fast direct modulation of the light source is possible. At this time, the pulse voltage may be about 2 Volts or less. When a DC bias voltage is applied to the first electrode Eand the second electrode E, the resonance frequency (or wavelength) and quality value of the light source may be controlled by using thermal expansion of the heterojunction structure HS by Joule heating of the graphene layer GR. In this case, the DC bias voltage may be about 5 Volts or more.

1 2 1 2 1 2 1 2 2 1 2 1 1 1 1 1 1 1 1 2 1 2 1 2 1 2 4 5 a a FIGS.and From a plan view, the heterojunction structure HS may include a first buffer area BR, a second buffer area BR, and an emission area LER between the first buffer area BRand the second buffer area BR. Here, a photonic crystal structure including a plurality of photonic crystal holes PCH may be provided in the emission area LER. The emission area LER may include a first area RGin which photonic crystal holes PCH are not provided and a second area RGsurrounding the first area RG, the second area RGin which photonic crystal holes PCH are provided. The photonic crystal holes PCH may be regularly arranged in the second area RG, and the first area RGmay be defined as an area in which a rule in which the photonic crystal holes PCH are arranged in the second region RGis broken. For example, the first area RGmay be located in the center part of the upper surface of the emission area LER. However, unlike shown in the drawing, the first area RGmay be provided in plural, and may be located in a place other than the center part. For example, 1 to 30 first areas RGmay be provided at different positions. By controlling the position of the first area RG, it is possible to determine the local light emission position of the light source according to the inventive concept. The arrangement of the plurality of photonic crystal holes PCH and the location of the first area RGwill be described in detail later with reference to. The emission area LER may be spaced apart from the first electrode Ein the first direction Dwith the first buffer area BRinterposed therebetween. In addition, the emission area LER may be spaced apart from the second electrode Ein the first direction Dwith the second buffer area BRinterposed therebetween. The first buffer area BRand the second buffer area BRmay prevent heat generated in the emission area LER from being transferred to the first electrode Eand the second electrode E.

1 1 2 1 1 2 1 1 1 The maximum length of the heterojunction structure HS in the first direction Dmay be defined as the first length L, and the maximum width of the heterojunction structure HS in the second direction Dmay be defined as the first width W. The contact resistance between the heterojunction structure HS and the first electrode Eand the second electrode Emay be determined through the first width W. For example, the first length Land the first width Wmay be about 2 μm to about 10 μm, respectively.

1 2 2 2 2 2 1 2 2 1 2 1 2 1 2 2 2 The length of the emission area LER in the first direction Dmay be defined as the second length L, and the width of the emission area LER in the second direction Dmay be defined as the second width W. For example, the second length Land the second width Wmay be about 1 μm to about 5 μm, respectively. For example, the emission area LER may have a rectangular upper surface having a constant length in the first direction Dand a constant width in the second direction D. The second length Lmay be smaller than the first length L, and the second width Wmay be smaller than the first width W. For this reason, the light source according to the inventive concept may operate stably. More specifically, since the second width Wof the emission area LER is smaller than the first width W, the light emission position may be localized. As the light emission position is localized, the quality value may increase, and as the quality value increases, the energy efficiency of the light source may increase. The operating current magnitude I of the light source according to the inventive concept may be proportional to the second width W. That is, it is possible to determine the operating current magnitude I of the light source through the second width W. The proportional relationship between the operating current magnitude I and the second width Wof the light source according to the inventive concept may be expressed by [Equation 1].

In [Equation 1], I is an operating current magnitude, and a is a proportional constant. The unit of the operating current magnitude is mA, and the unit of the proportional constant a is mA/μm. For example, the proportional constant a may be about 1 to 2.

2 1 1 2 2 2 2 In addition, since the second length Lof the emission area LER is smaller than the first length L, deformation and damage of the first electrode Eand the second electrode Emay be reduced by joule heating of the graphene layer GR. The operating voltage magnitude V of the light source according to the inventive concept may be proportional to the second length L. That is, the operating voltage magnitude V of the light source may be determined through the second length L. The proportional relationship between the operating voltage magnitude V and the second length Lof the light source according to the inventive concept may be expressed by [Equation 2].

In [Equation 2], V is an operating voltage magnitude, and β is a proportional constant. The unit of operating voltage magnitude is Volts, and the unit of proportional constant β is Volts/μm. For example, the proportional constant β may be about 1 to 5.

1 2 1 2 2 1 1 2 2 1 1 2 1 2 2 2 2 1 2 The width of the first buffer area BRin the second direction Dmay decrease toward the first direction D. Meanwhile, the width of the second buffer area BRin the second direction Dmay increase toward the first direction D. Each of the maximum widths of the first buffer area BRand the second buffer area BRin the second direction Dmay be substantially the same as the first width W. For example, the first buffer area BRand the second buffer area BRmay have a symmetrical shape with the emission area LER interposed therebetween. The minimum width of each of the first buffer area BRand the second buffer area BRin the second direction Dmay be substantially the same as the width of the emission area LER in the second direction D(i.e., the second width W). Unlike illustrated in the drawings, profiles of corner portions of the first buffer area BRand the second buffer area BRmay have a curved shape.

1 2 3 3 1 2 3 1 3 2 3 1 3 1 1 1 1 1 2 2 1 1 1 2 2 2 a a c c Also, in terms of a cross-sectional area, the heterojunction structure HS may include a first encapsulation layer N, a graphene layer GR, and a second encapsulation layer Nsequentially stacked in a third direction D. The thickness of the graphene layer GR in the third direction Dmay be smaller than the thickness of the first encapsulation layer Nand the second encapsulation layer Nin the third direction D. For example, the thickness of the first encapsulation layer Nin the third direction Dmay be smaller than the thickness of the second encapsulation layer Nin the third direction D. For example, the length of the heterojunction structure HS in the first direction Dmay decrease toward the third direction D. In this case, the maximum length of the first encapsulation layer Nin the first direction Dmay be substantially the same as the first length L. For example, the upper surface of the first portion Eof the first electrode Eand the upper surface of the first portion Eof the second electrode Emay be located at a lower level than the upper surface of the first encapsulation layer N. In addition, as an example, the lower surface of the third portion Eof the first electrode Eand the upper surface of the third portion Eof the second electrode Emay be coplanar with the upper surface of the second encapsulation layer N.

1 2 1 2 100 1 2 1 2 1 2 100 1 2 1 2 The photonic crystal holes PCH may pass through the first encapsulation layer N, the graphene layer GR, and the second encapsulation layer N. The photonic crystal holes PCH may penetrate the heterojunction structure HS to expose the side surfaces of each of the first encapsulation layer N, the graphene layer GR, and the second encapsulation layer Nand the upper surface of the substrate. The first encapsulation layer Nand the second encapsulation layer Nmay include, for example, hexagonal boron nitride (hBN). Hexagonal boron nitride (hBN) is stable at high temperatures and may have excellent sealing effects. Accordingly, the first encapsulation layer Nand the second encapsulation layer Nmay increase the life expectancy of the light source using the photonic crystal structure according to the inventive concept. In addition, the refractive index of hexagonal boron nitride (hBN) may be greater than that of silicon oxide or silicon nitride. Accordingly, the first encapsulation layer Nand the second encapsulation layer Nmay reduce optical waveguiding loss on the substrate. At this time, the junction of each of the graphene layer GR and the first encapsulation layer Nand the second encapsulation layer Nmay be a van der Waals heterostructure. Due to the heterogeneous bonding of the graphene layer GR and the first encapsulation layer Nand the second encapsulation layer N, the light source according to the inventive concept may emit light through strong light-material interaction at the bonding interface while maintaining excellent graphene properties.

3 FIG. 1 FIG. 1 2 FIGS.and is a cross-sectional view illustrating a structure of a light source using a photonic crystal structure according to an embodiment of the inventive concept, and corresponds to a cross-sectional view oftaken along line I-I′. Hereinafter, for convenience of description, descriptions of substantially the same matters as those described with reference towill be omitted.

3 FIG. 110 100 1 2 100 110 110 2 110 110 1 110 3 110 110 3 110 1 2 2 1 110 110 3 110 1 3 1 110 Referring to, an optical waveguidemay be provided between the heterojunction structure HS and the substrateor between the first electrode Eand the second electrode Eand the substrate. The optical waveguidemay include, for example, silicon or silicon nitride. The optical waveguidemay extend in the second direction D. A plurality of optical waveguidesmay be provided, and the plurality of optical waveguidesmay be spaced apart from each other in the first direction D. At least some of the optical waveguidesmay overlap the emission area LER in the third direction D. An empty space between the optical waveguidesmay be defined as a gap area GAP. For example, any one of the plurality of optical waveguidesmay overlap the entire emission area LER in the third direction D. That is, the length of any one of the optical waveguidesin the first direction Dmay be determined according to the second length Lof the emission area LER. Conversely, the second length Lof the emission area LER may be determined according to the length in the first direction Dof any one of the optical waveguides. However, unlike illustrated in the drawing, the plurality of optical waveguidesmay overlap a part of the emission area LER, respectively, in the third direction D. In addition, any one of the plurality of optical waveguidesmay overlap the first area RGin the third direction D. By controlling the location and number of the first area RG, coupling between the heterojunction structure HS of the light source and the optical waveguideaccording to the inventive concept may be improved.

3 FIG. 3 FIG. 1 2 110 110 1 2 In the structure of, when a DC bias voltage is applied to the first electrode Eand the second electrode E, the wavelength of the light source coupled to the optical waveguidemay be controlled using thermal expansion of the heterojunction structure HS by Joule heating of the graphene layer GR. In this case, the DC bias voltage may be about 5 Volts or more. In addition, in the structure of, an optical signal transmitted through the optical waveguidemay be detected or measured. More specifically, without applying a voltage to the first electrode Eand the second electrode E, voltage and current flowing through the graphene layer GR may be measured to detect or measure a specific wavelength of the optical signal. That is, the light source using the photonic crystal structure according to the inventive concept may be used as a photodetector.

4 a FIG. 4 b FIG. 4 FIG. a. is a plan view illustrating an emission area of a light source using a photonic crystal structure according to an embodiment of the inventive concept.is a graph for explaining the result of simulation of resonance frequency of a light source using a photonic crystal structure according to an embodiment of the inventive concept, and is a result according to the photonic crystal structure of

4 a FIG. 1 1 2 2 2 1 1 1 1 1 2 1 1 1 1 Referring to, a plurality of photonic crystal holes PCH penetrating the heterojunction structure HS may be provided. For example, the first area RGmay be provided on a center part of the upper surface of the heterojunction structure HS. The photonic crystal holes PCH may be arranged at regular intervals in the first direction Din the second area RG. In addition, the photonic crystal holes PCH may be arranged in a zigzag shape while going in the second direction Din the second area RG. For example, the size of the photonic crystal holes PCH may be constant. That is, the radius of each of the photonic crystal holes PCH may be the same as the first radius R. For example, the first radius Rmay be about 50 nm to about 150 nm. Preferably, the first radius Rmay be about 90 nm to 130 nm. Also, a distance between the centers of the photonic crystal holes PCH adjacent to each other may be defined as a first lattice constant LC. The size of the first lattice constant LCin the second area RGmay be constant. For example, the first lattice constant LCmay be about 300 nm to about 400 nm. Preferably, the first lattice constant LCmay be about 340 nm to about 380 nm. In this case, by adjusting the values of the first radius Rand/or the first lattice constant LC, the resonance frequency of the light source may be controlled.

4 b FIG. 4 a FIG. 4 b FIG. Referring to, the result of simulation of the resonance frequency according to the photonic crystal structure ofis shown. In the graph, the horizontal axis represents the emission wavelength of the light source, and the vertical axis represents the relative value of the intensity of the emitted light.shows that the lattice constant is finely adjusted due to thermal expansion according to the magnitude of the DC bias voltage, and accordingly, the resonance frequency of the light source may be controlled.

4 a FIG. 4 b FIG. 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 1 2 2 3 3 4 2 The simulation according to the photonic crystal structure ofshows the first to fourth resonance modes CM, CM, CM, and CM. The first to fourth resonance modes CM, CM, CM, and CMare resonance modes when the first to fourth DC bias voltages VDC, VDC, VDC, and VDCare applied, respectively.shows that the resonance mode moves according to the magnitudes of the first to fourth DC bias voltages VDC, VDC, VDC, and VDC(VDC<VDC<VDC<VDC). When the first DC bias voltage VDCis applied, the first resonance mode CMmay have a spectrum having a center wavelength of about 1542 nm, and when the second DC bias voltage VDCis applied, the second resonance mode CMmay have a spectrum having a center wavelength of about 1546 nm. In addition, when the third DC bias voltage VDCis applied, the third resonance mode CMmay have a spectrum having a center wavelength of about 1550 nm, and when the fourth DC bias voltage VDCis applied, the fourth resonance mode CMmay have a spectrum having a center wavelength of about 1554 nm. In this case, the center wavelength may mean a wavelength having the greatest intensity in the spectrum of emitted light.

1 1 1 2 3 4 1 2 3 4 1 1 2 3 4 Meanwhile, the intensity of the first blackbody radiation spectrum BBRmay increase according to a wavelength. The first blackbody radiation spectrum BBRmay have a wavelength band wider than that of each of the first to fourth resonance modes CM, CM, CM, and CM, and may not have a peak. That is, the spectrum of each of the first to fourth resonance modes CM, CM, CM, and CMmay have a Gaussian distribution having a relatively high quality value as compared to the first blackbody radiation spectrum BBR. Each of the first to fourth resonance modes CM, CM, CM, and CMmay have a quality value of about 200.

5 a FIG. 5 b FIG. 5 FIG. a. is a plan view illustrating an emission area of a light source using a photonic crystal structure according to an embodiment of the inventive concept.is a graph for explaining the result of simulation of resonance frequency of a light source using a photonic crystal structure according to an embodiment of the inventive concept, and is a result according to the photonic crystal structure of

5 a FIG. 1 2 3 1 3 1 2 1 1 2 2 3 3 1 2 3 1 2 3 1 1 3 1 2 2 3 2 2 2 2 1 2 2 2 3 2 1 2 3 2 Referring to, a plurality of photonic crystal holes PCH penetrating the heterojunction structure HS may be provided in the emission area LER. The emission area LER may include first to third hole areas HR, HR, and HR. For example, the first area RGmay be provided inside the third hole area HR. The outer boundary of the first hole area HRmay be substantially the same as the boundary of the second area RG. For example, the photonic crystal holes PCH may include first holes Hprovided inside the first hole area HR, second holes Hprovided inside the second hole area HR, and third holes Hprovided inside the third hole area HR. In this case, boundaries of the first to third hole areas HR, HR, and HRmay have a hexagonal shape. However, this is only an example, and the boundaries of the first to third hole areas HR, HR, and HRare not limited to a hexagonal shape and may have various shapes. For example, the first area RGmay be provided in a center part of the upper surface of the emission area LER. More specifically, the first area RGmay be provided in the center part of the third hole area HR. The size of the first holes Hmay be larger than the size of the second holes H. Also, the size of the second holes Hmay be larger than the size of the third holes H. That is, the size of the photonic crystal holes PCH may gradually decrease as the edge of the emission area LER goes toward the center part. The distance between the centers of the photonic crystal holes PCH adjacent to each other may be defined as a second lattice constant LC. Since the size of the photonic crystal holes PCH is not constant, the size of the second lattice constant LCmay not be constant. For example, the second lattice constant LCmay be about 300 nm to about 400 nm. Preferably, the second lattice constant LCmay be about 310 nm to about 350 nm. In addition, for example, the radius of each of the first holes Hmay be about 0.2 times the second lattice constant LC, the radius of each of the second holes Hmay be about 0.25 times the second lattice constant LC, and the radius of each of the third holes Hmay be about 0.3 times the second lattice constant LC. That is, the sizes of the first to third holes H, H, and Hmay be determined in proportion to the second lattice constant LC. However, unlike illustrated in the drawing, four or more hole areas are provided in the emission area LER, and photonic crystal holes PCH in each of the hole areas may have different sizes.

5 a FIG. 2 That is, according to the photonic crystal structure of, the resonance frequency of the light source may be controlled by adjusting the value of the second lattice constant LC. In addition, a narrower emission spectrum may be obtained due to the stepwise modification of the size of the photonic crystal holes PCH. Due to the narrower emission spectrum, the quality value may increase, and as the quality value increases, the energy efficiency of the light source may increase.

5 b FIG. 5 a FIG. 5 b FIG. Referring to, a result of simulation of resonance frequencies according to the photonic crystal structure ofis shown. In the graph, the horizontal axis represents the emission wavelength of the light source, and the vertical axis represents the relative value of the intensity of the emitted light.shows that the lattice constant is finely adjusted due to thermal expansion according to the magnitude of the DC bias voltage, and accordingly, the resonance frequency of the light source may be controlled.

5 a FIG. 5 6 7 8 5 6 7 8 5 6 7 8 5 5 6 7 8 5 6 7 8 5 5 6 6 7 7 8 8 b The simulation according to the photonic crystal structure ofshows fifth to eighth resonance modes CM, CM, CM, and CM. The fifth to eighth resonance modes CM, CM, CM, and CMare resonance modes when the fifth to eighth DC bias voltages VDC, VDC, VDC, and VDCare applied, respectively.shows that the resonance mode moves according to the magnitudes of the fifth to eighth DC bias voltages VDC, VDC, VDC, and VDC(VDC<VDC<VDC<VDC). When the fifth DC bias voltage VDCis applied, the fifth resonance mode CMmay have a spectrum having a center wavelength of about 1542 nm, and when the sixth DC bias voltage VDCis applied, the sixth resonance mode CMmay have a spectrum having a center wavelength of about 1546 nm. In addition, when the seventh DC bias voltage VDCis applied, the seventh resonance mode CMmay have a spectrum having a center wavelength of about 1550 nm, and when the eighth DC bias voltage VDCis applied, the eighth resonance mode CMmay have a spectrum having about 1554 nm as a center wavelength. In this case, the center wavelength may mean a wavelength having the greatest intensity in the spectrum of emitted light.

2 2 5 6 7 8 5 6 7 8 2 5 6 7 8 4 a FIG. 5 a FIG. Meanwhile, the intensity of the second blackbody radiation spectrum BBRmay increase according to a wavelength. The second blackbody radiation spectrum BBRmay have a wavelength band wider than that of each of the fifth to eighth resonance modes CM, CM, CM, and CM, and may not have a peak. That is, the spectrum of each of the fifth to eighth resonance modes CM, CM, CM, and CMmay have a Gaussian distribution having a relatively high quality value as compared to the second blackbody radiation spectrum BBR. Each of the fifth to eighth resonance modes CM, CM, CM, and CMmay have a quality value of about 1385. Compared with the resonance mode according to the photonic crystal structure of, the resonance mode according to the photonic crystal structure ofmay have a higher quality value.

In the above, embodiments of the inventive concept have been described with reference to the accompanying drawings, and those of ordinary skill in the art to which the inventive concept pertains will be able to understand that the inventive concept may be implemented in other specific forms without changing the technical spirit or essential features. Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects.